The present invention relates to a method for manufacturing a semiconductor device by laminating and forming thin films on an insulating amorphous material and on an insulating crystallized material.
When a semiconductor device is to be formed on a substrate, such insulating amorphous material as quartz and such insulating crystallized material as what glass is treated by heat to create a crystal nucleus and to grow crystal to deposit the crystal, for example, are used for the substrate.
Moreover, needs for such semiconductor devices as a large size liquid crystal panel or an image sensor utilized in equipments such as a facsimile scanner is increasing lately.
Due to that, it has become necessary to lower the cost of those semiconductor devices by manufacturing them by increasing their yield. In order to manufacture semiconductor devices by increasing their yield, a precision of technique for aligning a mask pattern of a coating film to be formed next to a pattern of a coating film already formed on a substrate has to be improved.
In a case of forming a thin film transistor, an insulating non-crystal material having an excellent heat resistance such as quartz is used as the substrate since such high temperature heat treatments as follows are carried out in the manufacturing process: 1) poly-crystallization of an amorphous layer mainly of silicon, 2) formation of a gate oxide film, and 3) implantation of ions. However, a manufacturing cost of such insulating amorphous materials having an excellent heat resistance as quartz is high, so that it is a factor that hampers the realization of low cost semiconductor devices especially when a semiconductor device is to be formed on a large size substrate. Then a method for fabricating a semiconductor device on a crystallized glass, which is cheaper than quartz, as an insulating substrate material used for forming semiconductor devices has been drawing an attention and its studies are being conducted.
However, crystallized glass has a property to expand and contract when treated by heat and its degree of expansion-contraction is asymmetrical to the forming direction when the substrate is manufactured (the substrate has an anisotropy in a degree of expansion-contraction), e.g. to the solidification direction for forming the substrate by melting once and solidifying it and to the crystallization direction into which crystal is deposited, so that when a mask pattern for a film which is to be formed next to a pattern of a film already formed on the substrate is superimposed, the patterns are dislocated and it has been difficult to fabricate a semiconductor device by laminating thin films having very fine patterns. Therefore, even if such semiconductor device may be fabricated, high precision alignment has been impossible in photolithographic process, thereby causing such problems that yield is lowered due to the dislocation of the alignment and that thereby the cost is increased.
Accordingly, it is an object of the present invention to solve the aforementioned problems by providing a method for manufacturing a semiconductor device which allows to form a semiconductor device in a high precision alignment on such substrate that has an anisotropy in a degree of expansion-contraction when treated by heat like an insulating amorphous material and an insulating crystallized glass.